Assuming we are talking about a checking account, the UCC indicates that a person's signature, one capable of making him or her responsible on an instrument, is whatever he says it is. For example, "X" can be a valid signature.
If your institution wishes to assert that "JRDJ" alone would increase the risk of forgery and, thus, would be unacceptable to you, then so be it. I'm really hoping that the CSR sought advice before opening the account.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.